JP3576432B2 - Silicon carbide film and method of manufacturing the same - Google Patents

Description

【００３０】
【表２】

【００３１】
各基板上に成長させたＳｉＣについて、反位相領域境界面の密度を測定したところ、表３に示す結果を得た。
なお、反位相領域境界面の密度は、炭化珪素表面をＡＦＭ観察して求めた。この際、炭化珪素の表面を熱酸化処理しさらに熱酸化膜を除去することにより反位相境界を顕在化させたあとに観察を行った。
【００３２】
【表３】

【００３３】
表３に示すオフ角度と反位相領域境界面密度との関係から、オフ角導入による反位相領域境界面密度の減少が確認されるものの、完全な解消には至っていないことがわかる。
【００３４】
オフ角４°の基板上に成長させたＳｉＣ膜表面の走査型電子顕微鏡写真を図４に示し、オフ角無しの基板上に成長させたＳｉＣ膜表面の走査型電子顕微鏡写真を図５に示す。
図４及び図５から、オフ角導入によりテラス面積の拡大が確認されてステップフローモードでのＳｉＣ成長が支配的となっており、面欠陥の伝搬方位が特定の結晶面内に限定されていることがわかる。
【００３５】
実施例１
Ｓｉ（００１）面を被成長基板とし、基板表面を熱酸化後、フォトリソグラフィー技術を用いて基板表面上に１．５μｍ幅、長さ６０ｍｍ、厚さ１μｍのライン＆スペースパターンをレジストにて形成した。ただし、ライン＆スペースパターンの方向は［１１０］方位に平行にした。この基板を表４に示す条件でホットプレートを用いて加熱することにより、ライン＆スペースレジストパターンがラインと直交する方向に広がって変形し、起伏の頂点と底が滑らかな曲線で繋がった波面状の断面のレジストパターン形状を得た。このレジストパターンの断面形状（起伏）及び平面形状（ライン＆スペース）をドライエッチングにてＳｉ基板に転写した。
レジストを過酸化水素と硫酸の混合液中で除去した後（図６）、３Ｃ−ＳｉＣの成長を実施した。ＳｉＣの成長は、基板表面の炭化工程と、原料ガスの交互供給によるＳｉＣ成長工程に分けられる。ＳｉＣ成長工程の詳細条件を表５に示す。なお、炭化工程の詳細条件は表１と同様とした。
【００３６】
【表４】

【００３７】
【表５】

【００３８】
ＳｉＣ成長工程において、原料ガスの供給サイクル数を変化させることにより、ＳｉＣの膜厚を変化させて、最表面に現れる反位相領域境界面の密度を上記と同様にして測定したところ、表６に示す結果を得た。
【００３９】
【表６】

【００４０】
表６に示すＳｉＣ膜厚と反位相領域境界面密度との関係から、起伏形状を有するＳｉ基板上にエピタキシャル成長するＳｉＣの膜厚が、起伏頂部の間隔３．０μｍの１／√２倍である２．１μｍを超えたところでの反位相領域境界面の減少が大きく、従来法である表３の数値と比較して本発明の有効性が顕著であることがわかる。
【００４１】
実施例２
Ｓｉ（００１）面を被成長基板とし、フォトリソグラフィー技術を用いて基板表面上に１．５μｍ幅、長さ６０ｍｍ、厚さ１μｍのライン＆スペースパターンをレジストにて形成した。ただし、ライン＆スペースパターンの方向は［１１０］方位に平行にした。この基板を表７に示す条件でホットプレートを用いて加熱しレジストを軟化させてレジストパターンの断面形状を変化させた。このレジストパターンの断面形状（起伏）及び平面形状（ライン＆スペース）をドライエッチングにてＳｉ基板に転写した。
レジストを過酸化水素と硫酸の混合液中で除去した後、３Ｃ−ＳｉＣの成長を実施した。ＳｉＣの成長は、基板表面の炭化工程と、原料ガスの交互供給によるＳｉＣ成長工程に分けられる。なお、炭化工程の詳細条件は表１と同様とし、ＳｉＣ成長工程の詳細条件は表５と同様とした。
【００４２】
【表７】

【００４３】
レジストパターンの加熱温度を１５０℃〜２００℃の間で変化させて、起伏の傾斜角θを変化させた各基板上にそれぞれ成長させた３Ｃ−ＳｉＣについて、最表面に現れる反位相領域境界面の密度を上記と同様にして測定したところ、表８に示す結果を得た。
【００４４】
【表８】

【００４５】
表８に示す起伏の斜度と反位相領域境界面密度との関係から、起伏の傾斜角θが、特に（１１１）面のなす角である５４．７°未満であって１°以上である場合に反位相領域境界面の密度の減少が確認できる。さらに、従来法である表３の数値と比較して、同じオフ角であっても本発明の如く起伏加工基板上へ成長させた３Ｃ−ＳｉＣは反位相領域境界面密度が大幅に減少又は解消しており、本発明の有効性が顕著であることがわかる。
【００４６】
実施例３
Ｓｉ（００１）面を被成長基板とし、フォトリソグラフィー技術を用いて基板表面上に１．５μｍ幅、長さ６０ｍｍ、厚さ１μｍのライン＆スペースパターンをレジストにて形成した。ただし、ライン＆スペースパターンの方向に関して、［１１０］方位とライン＆スペースパターンの方向との交差角度ω（図７参照）を表９に示すように変化させた。その後、表４に示す加熱条件でホットプレートを用いて基板を加熱しレジストを軟化させてレジストパターンの断面形状を変形させた。このレジストパターン形状をドライエッチングにてＳｉ基板に転写した。
レジストを過酸化水素と硫酸の混合液中で除去した後、３Ｃ−ＳｉＣの成長を実施した。ＳｉＣの成長は、基板表面の炭化工程と、原料ガスの交互供給によるＳｉＣ成長工程に分けられる。なお、炭化工程の詳細条件は表１と同様とし、ＳｉＣ成長工程の詳細条件は表２と同様とした。
【００４７】
交差角度ωを変化させた各基板上にそれぞれ成長させた３Ｃ−ＳｉＣについて、最表面に現れる反位相領域境界面の密度を上記と同様にして測定したところ、表９に示す結果を得た。
【００４８】
【表９】

【００４９】
表９に示す交差角度ωと反位相領域境界面密度との関係から、ライン＆スペースパターンの方向が、［１１０］方位に配向するにしたがい、反位相領域境界面の密度の減少が確認できる。さらに、従来法である表３の数値と比較して、反位相領域境界面密度が大幅に減少又は解消しており、本発明の有効性が顕著であることがわかる。
【００５０】
実施例４
実施例１〜３ではライン幅とスペース幅の等しいライン＆スペースパターンを有するマスクを使用して、凹部、凸部の割合が等しい起伏断面パターン持つ基板を作製し、その上に３Ｃ−ＳｉＣの成長を行った。そこで実施例４では、凸部の密度を減少させたパターンとして、ライン幅１．５μｍ、スペース幅がライン幅のそれぞれ２倍、４倍、８倍、１６倍であるライン＆スペースパターンをそれぞれ用いて基板加工を行い、その上に３Ｃ−ＳｉＣの成長を行った。基板加工条件、ＳｉＣ成長条件は、ともに実施例３と同一である。ただし、起伏の傾斜角は４°とした。
起伏凹部の密度を変化させたそれぞれのパターンに対する反位相領域境界面の密度を上記と同様にして測定したところ、表１０に示す結果を得た。なお、比較として、ライン幅、スペース幅がともに１．５μｍのパターンを用いた場合の反位相領域境界面密度、及びライン幅が無限大（∞）に広がった極限とみなせる起伏無しのＳｉ（００１）基板（オフ角度０°）を用いた場合の反位相領域境界面密度についても同様にして測定し表１０に示した。
【００５１】
【表１０】

【００５２】
表１０から、起伏凸部の間隔が広くなり、起伏密度が減少するほど反位相領域境界面密度の増大が確認できる。さらに、従来法である表３の数値と比較して、反位相領域境界面密度が大幅に減少又は解消しており、本発明の有効性が顕著であることがわかる。
【００５３】
実施例５
実施例１〜４では基板断面が波状の構造に関してのみ説明を行ってきた。本発明の有効性が波状型以外の構造に関しても保持されることは図３の説明からも明らかである。実際に以下の方法により、断面が鋸歯状の起伏加工をＳｉ（００１）面上に施し、その基板上への３Ｃ−ＳｉＣの成長を行った。
詳しくは、Ｓｉ（００１）面を被成長基板とし、フォトリソグラフィー技術を用いて基板表面上に１．５μｍ幅、長さ６０ｍｍ、厚さ１μｍのライン＆スペースパターンをレジストにて形成した。ただし、ライン＆スペースパターンの方向は［１１０］方位と平行とした。このレジストパターン形状をドライエッチングにてＳｉ基板に転写した。レジストを過酸化水素と硫酸の混合液中で除去した後、基板をＫＯＨ水溶液に浸漬してウエットエッチングを行った。ウエットエッチングの条件を表１１に示す。ウエットエッチングの結果、傾斜角１°、１０°、５５°の鋸歯状の起伏を有する単結晶Ｓｉ（００１）面が得られた（図８参照）。なお、図８において、４はウエットエッチング前の基板断面構造を示し、５はウエットエッチング後の鋸歯状の基板断面構造を示す。
【００５４】
【表１１】

【００５５】
上記基板上に３Ｃ−ＳｉＣの成長を実施した。ＳｉＣの成長は、基板表面の炭化工程と、原料ガスの交互供給によるＳｉＣ成長工程に分けられる。なお、炭化工程の詳細条件は表１と同様とし、ＳｉＣ成長工程の詳細条件は表２と同様とした。
各基板上にそれぞれ成長させたＳｉＣについて、最表面に現れる反位相領域境界面の密度を上記と同様にして測定したところ、表１２に示す結果を得た。
【００５６】
【表１２】

【００５７】
表１２から、基板断面が鋸歯状の起伏構造であっても本発明が有効性であることがわかる。また、この基板作製方法が本発明の有効性を発揮するのに適することがわかる。
【００５８】
実施例６
実施例１〜５はいずれもＳｉ（００１）面基板上に立方晶炭化珪素膜を成長させたものである。実施例６では被成長基板として、単結晶の立方晶炭化珪素（単結晶３Ｃ−ＳｉＣ）の（００１）面上に［１１０］方位に平行に伸びる起伏を具備した基板、及び、単結晶の六方晶炭化珪素の（１，１，−２，０）面上に［０，０，０，１］方位に平行に伸びる起伏を具備した基板、をそれぞれ用いて、それぞれの基板表面上に立方晶炭化珪素膜もしくは六方晶炭化珪素膜の成長を行った。
その結果、実施例１〜５と同様に本発明の有効性が確認された。
【００５９】
実施例７
実施例１〜６はいずれも起伏の作製方法としてＳｉ基板（００１）表面をリソグラフィー技術を用いてエッチングする方法を採用しているが、本発明の有効性をもたらす被成長基板表面の起伏作製方法はエッチング以外の他の手法にて行うことができる。実施例７ではその一例を挙げる。
Ｓｉ（００１）面を基板とし、この表面を熱酸化して３０００オングストロームのＳｉ酸化膜（ＳｉＯ_２膜）を形成した。そしてこの熱酸化膜上にフォトリソグラフィー技術を用いて１．５μｍ幅、長さ６０ｍｍ、厚さ１μｍのライン＆スペースパターンをレジストにて形成した。ただし、ライン＆スペースパターンの方向は［１１０］方位と平行とした。このレジストパターン形状をドライエッチングにて熱酸化膜に転写し、ストライプ状のＳｉＯ_２パターン及びＳｉ露出部を設けた。レジストを過酸化水素と硫酸の混合液中で除去した後、この基板上に図９に示すようにＳｉの選択的ホモエピタキシャル成長を実施した。ＳｉＣ成長工程の詳細条件を表１３に示す。なお、図９において、６はストライプ状のＳｉＯ_２パターン、７は選択的ホモエピタキシャル成長したＳｉ層を示す。
【００６０】
【表１３】

【００６１】
Ｓｉ成長の結果、傾斜角５５°の起伏を具備する単結晶Ｓｉ（００１）面が得られた。この基板表面へ３Ｃ−ＳｉＣの成長を行い、反位相領域境界面密度が大幅に減少することを確認した。
【００６２】
実施例８
実施例８では、Ｓｉ（１００）基板表面に、［１１０］方向に平行に研磨処理を施す方法で、［１１０］方向に平行な起伏形成基板を作製することを試みた。研磨には、市販されている約１５ｍｍφ径のダイヤモンドスラリー（エンギス社製：ハイプレス）と市販の研磨パッド（エンギス社製：Ｍ４１４）を用いた。
パッド上にダイヤモンドスラリーを一様に浸透させ、パッド上にＳｉ（１００）基板を置き、０．１〜０．２ｋｇ／ｃｍ^２の圧力をＳｉ（１００）基板全体に加えながら、［１１０］方向に平行にパッド上約２０ｃｍの距離を３００回往復させて一方向研磨処理を施した。Ｓｉ（１００）基板表面には［１１０］方向に平行な研磨傷（スクラッチ）が無数に形成された。
一方向研磨処理を施したＳｉ（１００）基板表面に研磨砥粒などが付着しているので、ＮＨ_４ＯＨ＋Ｈ_２Ｏ_２＋Ｈ_２Ｏ混合溶液（ＮＨ_４ＯＨ：Ｈ_２Ｏ_２：Ｈ_２Ｏ＝４：４：１の割合で液温６０℃）にて洗浄し、Ｈ_２ＳＯ_４＋Ｈ_２Ｏ_２溶液（Ｈ_２ＳＯ_４：Ｈ_２Ｏ_２＝１：１の割合で液温８０℃）とＨＦ（１０％）溶液に交互に３回ずつ浸して洗浄し、最後に純水でリンスした。
洗浄した後、一方向研磨処理基板上に熱酸化膜を約５０００オングストローム厚形成した。熱酸化膜をＨＦ１０％溶液により除去した。研磨を施しただけであると、基板表面はスクラッチ以外にも細かい凹凸や欠陥が多く被成長基板としては用い難い。しかし、熱酸化膜を一度形成して、改めて酸化膜を除去することで、基板表面の細かい凹凸が除去されて非常にスムーズなアンジュレーション（起伏）面を得ることができた。波状断面を見ると波状凹凸の大きさは不安定で不規則であるが、密度は高い。少なくとも水平な面はない。常に起伏の状態にある。平均すると、溝の深さは３０〜５０ｎｍ、幅は０．５〜１．５μｍ程度であった。斜度は３〜５度であった。
この基板を用いてＳｉＣ膜を基板上に作製した。結果は、［１１０］に平行な起伏形成基板の効果が得らた。すなわち、反位相境界面の欠陥は大幅に減少する。
例えば、未研磨のＳｉ基板上に成長したＳｉＣ膜の反位相境界面密度は８×１０^９個／ｃｍ^２であるのに対し、今回の一方向研磨を施したＳｉ基板上に成長したＳｉＣ膜の反位相境界面欠陥密度は０〜１個／ｃｍ^２となる．砥粒サイズに対しての起伏形状と反位相境界面欠陥密度は表１４に示す通りになる。また、研磨回数に対しての起伏の密度と反位相境界面欠陥密度は表１５に示す通りになる。
【００６３】
【表１４】

【表１５】

【００６４】
なお実施例８では、研磨剤としてダイヤモンドスラリー１５μｍφサイズのものを用いたが、砥粒のサイズや砥粒の種類はこの限りではない。パッドも上記の限りではない。研磨時の基板とパッド間の負荷圧力、研磨速度や回数なども上記に限らない。また、実施例８ではＳｉ（１００）を用いたが、立方晶ＳｉＣ、六方晶ＳｉＣを用いても、上記と同様の結果が得られることは言うまでもない。
【００６５】
以上実施例をあげて本発明を説明したが、本発明は上記実施例に限定されるものではない。
【００６６】
例えば、炭化珪素膜の成膜条件や膜厚等は実施例のものに限定されない。
【００６７】
また、被成長基板としては、例えば、炭化珪素、サファイヤなどの単結晶基板等を使用できる。
【００６８】
珪素の原料ガスとしては、ジクロルシラン（ＳｉＨ_２Ｃｌ_２）を使用したが、ＳｉＨ_４、ＳｉＣｌ_４、ＳｉＨＣｌ_３などのシラン系化合物ガスを使用することもできる。また、炭素の原料ガスとしては、アセチレン（Ｃ_２Ｈ_２）を使用したが、ＣＨ_４、Ｃ_２Ｈ_６、Ｃ_３Ｈ_８などの炭化水素ガスを使用することもできる。
【００６９】
なお、炭化珪素のエピタキシャル成長法は、膜内面欠陥の伝搬方位を特定の結晶面内に限定し得る方法であれば良く、気相化学堆積（ＣＶＤ）法の他に、液相エピタキシャル成長法、スパッタリング法、分子線エピタキシー（ＭＢＥ）法などを使用することもできる。また、ＣＶＤ法の場合、原料ガスの交互供給法でなく、原料ガスの同時供給法を使用することもできる。
【００７０】
上記本発明方法によって被成長基板上に形成された炭化珪素膜は、この炭化珪素膜表面を絶縁体と接合し、被成長基板を除去した後、炭化珪素膜の欠陥層（被成長基板側の反位相領域境界面密度を有する部分）を除去することで、絶縁体上に半導体薄膜を形成した構造のＳＯＩ（ｓｅｍｉｃｏｎｄｕｃｔｏｒ−ｏｎ−ｉｎｓｕｌａｔｏｒ）構造とすることができる。
【００７１】
ここで、炭化珪素膜と絶縁体との接合は、例えば、陽極接合、低融点ガラスによる接着、直接接合、又は、接着剤による接合などの方法によって行うことができる。陽極接合は、電荷移動可能なイオンを含むガラス（例えば、ケイ酸塩ガラス、ホウケイ酸塩ガラス、ホウ酸塩ガラス、アルミノケイ酸塩ガラス、リン酸塩ガラス、フッリン酸塩ガラスなど）と炭化珪素膜とを接触させた後、電界を印加することで接合する方法である。この場合、接合温度は２００〜３００℃、印加電圧は５００〜１０００Ｖ、荷重は５００〜１０００ｇ／ｃｍ^２程度である。低融点ガラスによる接着は、炭化珪素膜表面上にスパッタリング法などにより低融点ガラスを堆積させ、荷重及び熱を加えて、ガラス同士を接着する方法である。直接接合は、炭化珪素膜を直接ガラスに静電気力により接触、結合させ、その後、荷重及び熱を加えて界面における結合を強化する方法である。
【００７２】
被成長基板の除去は、例えば、ウエットエッチングなどにより行うことができる。例えば、珪素基板の除去は、ＨＦとＨＮＯ_３の混酸（ＨＦ：ＨＮＯ_３＝７：１）に浸漬することで行うことができる。
【００７３】
欠陥層の除去は、炭化珪素膜の基板界面近傍に反位相境界が高密度で存在している欠陥層を除去する目的で行う。欠陥層の除去は、例えば、ドライエッチングなどにより行うことができる。例えば、ＣＦ_４（４０ｓｃｃｍ）、Ｏ_２（１０ｓｃｃｍ）をエッチングガスとし、ＲＦパワー３００Ｗで反応性イオンエッチングを行うことで欠陥層を除去できる。
【００７４】
ＳＯＩ構造体（基板）の用途としては、例えば、半導体用基板、ＴＦＴ液晶用基板などにおける透明導電膜、光磁気記録媒体におけるカー効果用の誘電層、マイクロマシン、各種センサー（応力センサーなど）、Ｘ線透過膜などが挙げられる。
【００７５】
【発明の効果】
以上説明したように本発明の炭化珪素の製造方法によれば、反位相領域境界面を効果的に低減又は消滅させた炭化珪素膜が得られる。
また、本発明の炭化珪素膜は、結晶境界密度が小さいため非常に優れた電気的特性を有し、各種電子素子などとして広く有用である。
【図面の簡単な説明】
【図１】オフ角を付与したＳｉ基板上への３Ｃ−ＳｉＣ成長に伴う反位相領域境界面の発生、消滅を説明するための模式的断面図である。
【図２】［１，−１，０］方位に平行な起伏を付与した単結晶Ｓｉ（００１）面基板を示す斜視図である。
【図３】起伏を付与したＳｉ（００１）面基板上への３Ｃ−ＳｉＣ成長に伴う反位相領域境界面の消滅を説明するための模式的断面図である。
【図４】オフ角４°の基板上に成長させたＳｉＣ膜表面の走査型電子顕微鏡写真である。
【図５】オフ角無しの基板上に成長させたＳｉＣ膜表面の走査型電子顕微鏡写真である。
【図６】起伏を付与したＳｉ基板の走査型電子顕微鏡写真である。
【図７】起伏パターンの方向を［１１０］方位からずらして加工したＳｉ基板を模式的に示す斜視図である。
【図８】鋸歯状の起伏を付与したＳｉ基板表面を模式的に示す断面図である。
【図９】エッチング以外の方法で起伏を作製する方法を説明するための模式的断面図である。
【符号の説明】
１ Ｓｉ基板の単原子ステップにて発生した反位相領域境界面
２ 反位相領域境界面会合点
３ Ｓｉ基板表面テラスにて発生した反位相領域境界面
θ オフ角度
φ Ｓｉ（００１）面と反位相領域境界面のなす角（５５°）
Ｗ 起伏頂部の間隔
ω 交差角度
４ ウエットエッチング前の基板断面構造
５ ウエットエッチング後の鋸歯状の基板断面構造
６ ストライプ状のＳｉＯ_２パターン
７ 選択的ホモエピタキシャル成長したＳｉ層[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a single crystal silicon carbide film or the like as an electronic material, and more particularly to a silicon carbide having a low defect density which is preferable for manufacturing a semiconductor device, a method for manufacturing the same, and the like.
[0002]
[Prior art]
Conventionally, the growth of silicon carbide (SiC) has been classified into bulk growth by sublimation and formation of a thin film by epitaxial growth on a substrate.
[0003]
In bulk growth by the sublimation method, 6H-SiC and 4H-SiC, which are crystal polymorphs of a high-temperature phase, can be grown, and a substrate of SiC itself has been realized. However, there are many defects (micropipes) introduced into the crystal, and it is difficult to increase the substrate area.
[0004]
On the other hand, when the epitaxial growth method on a single crystal substrate is used, the controllability of impurity addition is improved, the substrate area is increased, and the micropipes, which are problems in the sublimation method, are reduced. However, in the epitaxial growth method, there is often a problem that the stacking fault density increases due to a difference in lattice constant between the substrate material and the silicon carbide film. In particular, since Si generally used as a substrate to be grown has a large lattice mismatch with SiC, generation of twins (Twin) and anti-phase region boundary (APB) in the SiC growth layer occurs. , Which impair the characteristics of SiC as an electronic element.
[0005]
As a method of reducing plane defects in the SiC film, for example, a step of providing a growth region on a substrate to be grown, and a step of forming a silicon carbide single crystal in the growth region to a thickness specific to the growth plane orientation of the substrate. A technique has been proposed that includes a step of growing the same or more, and reduces the surface defects after a specific thickness (Japanese Patent Publication No. 6-41400). However, since the two types of anti-phase regions included in SiC have a characteristic of expanding in directions orthogonal to each other with an increase in the thickness of SiC, the anti-phase region boundary surface can be effectively formed. It cannot be reduced. Furthermore, since the orientation of the superstructure formed on the grown SiC surface cannot be arbitrarily controlled, for example, when discrete growth regions are coupled with each other during growth, a new antiphase An area boundary surface is formed, and electrical characteristics are impaired.
[0006]
[Problems to be solved by the invention]
As a method of effectively reducing the anti-phase region boundary surface, K.K. Shibahara et al. Proposed a growth method on a Si (100) surface substrate whose surface normal axis was slightly inclined from [001] to [110] direction (introducing an off-angle) (Applied Physics Letter, vol. 50). 1987, p. 1888). In this method, since the atomic-level steps are introduced at equal intervals in one direction by imparting a slight inclination to the substrate, a plane defect in a direction parallel to the introduced steps propagates, while the introduced steps are formed. This has the effect of suppressing the propagation of surface defects in a direction perpendicular to the plane (a direction crossing the step). Therefore, of the two types of anti-phase regions included in the film, the anti-phase region that expands in a direction parallel to the introduced step is one of the two types of anti-phase regions that expands in the orthogonal direction. Since the enlargement is performed preferentially as compared with the phase region, the boundary surface of the anti-phase region can be effectively reduced. However, as shown in FIG. 1, this method causes an undesired generation of the anti-phase region boundary surface 1 due to an increase in the step density of the SiC / Si interface. There is a problem that does not reach. In FIG. 1, reference numeral 1 denotes an antiphase region boundary generated at a single atom step of the Si substrate, 2 denotes an antiphase region boundary meeting point, 3 denotes an antiphase region boundary generated at the Si substrate surface terrace, θ indicates the off-angle, and φ indicates the angle (54.7 °) formed between the Si (001) plane and the anti-phase region boundary surface. The anti-phase region boundary surface 3 generated on the Si substrate surface terrace has the anti-phase Although it disappears at the region boundary surface meeting point 2, the antiphase region boundary surface 1 generated in the single atom step of the Si substrate has no association partner and does not disappear.
[0007]
The present invention has been made under the above-described background, and has as its object to provide a silicon carbide film or the like in which an anti-phase region boundary surface is effectively reduced or eliminated.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has the following constitution.
[0009]
(Configuration 1) A method for producing a silicon carbide film in which silicon carbide is epitaxially grown on a single crystal substrate surface while inheriting its crystal orientation,The anti-phase region boundary surfaces in the silicon carbide layer introduced unintentionally (generated at the step) by the step on the substrate surface are brought into association with each other.A method of manufacturing a silicon carbide film, comprising: providing a plurality of undulations extending in one direction parallel to all or a part of the substrate surface, and growing silicon carbide on the substrate surface.
[0010]
(Structure 2) A method for manufacturing a silicon carbide film according to structure 1, wherein an epitaxial growth mechanism capable of limiting the propagation orientation of a plane defect generated in the silicon carbide film to a specific crystal plane during growth is used. .
[0011]
(Configuration 3) When the average value of the distance between the tops of the undulations on the substrate surface is W, the thickness of the silicon carbide film is W / Ｗ2 (= 2^1/23.) The method for manufacturing a silicon carbide film according to Configuration 1 or 2, wherein the thickness is not less than the above.
[0012]
(Structure 4) The interval between the tops of the undulations on the substrate surface is 0.01 μm or more and 10 μm or less, the height difference of the undulations is 0.01 μm or more and 20 μm or less, and the slope of the undulations is 1 ° or more and 55 °. 4. The method for manufacturing a silicon carbide film according to Configurations 1 to 3, wherein:
[0013]
(Structure 5) Structures 1 to 4, wherein the substrate is single crystal SiC, the surface of the substrate is a (001) plane, and the surface has undulations extending parallel to the [110] direction. The method for producing a silicon carbide film according to the above.
[0014]
(Structure 6) The structure 1 wherein the substrate is single crystal 3C-SiC, the surface of the substrate is a (001) plane, and the surface has undulations extending parallel to the [110] direction. 5. The method for producing a silicon carbide film according to any one of items 1 to 4.
[0015]
(Structure 7) The substrate is hexagonal single-crystal SiC, the substrate surface is a (1,1, -2,0) plane, and the surface has a [1, -1,0,0] orientation or [ 5. The method for manufacturing a silicon carbide film according to Configurations 1 to 4, wherein the silicon carbide film has undulations extending parallel to the [0,0,0,1] direction.
[0016]
(Structure 8) The method for manufacturing a silicon carbide film according to any one of structures 1 to 7, wherein the cross section of the substrate has a wavy structure or the cross section has a serrated shape..
(Configuration 9) The method of manufacturing a silicon carbide film according to Configurations 1 to 8, wherein steps of orienting the substrate surface in a mirror-symmetric direction are introduced at a statistically balanced density..
(Constitution10) Configurations 1 to9A silicon carbide film manufactured using the method described in the above.
[0017]
(Constitution11A) having a structure in which a plurality of undulations extending parallel to one direction formed on the whole or a part of the surface of the single crystal substrate are used as steps, and epitaxial growth is performed by a method capable of limiting the propagation direction of film inner surface defects to a specific crystal plane; A silicon carbide film characterized by the following.
[0018]
[Action]
[0019]
According to Configuration 1, the surface of the silicon carbide growth substrate is provided with a plurality of undulations extending in parallel in one direction, so that the K.V. The effect of introducing the off-angle shown by Shibahara et al. Can be obtained. Furthermore, in the present invention, since the steps of the silicon carbide growth substrate surface oriented in a mirror-symmetrical orientation are introduced at a statistically balanced density, the silicon carbide unintentionally introduced by the growth substrate surface steps Anti-phase region boundaries in the layer are effectively associated with each other, and a silicon carbide film in which the anti-phase region boundary is completely eliminated can be obtained. Furthermore, according to the present invention, since the individual growth regions are all in-phase regions that expand in the same direction due to the effect of introducing the off-angle, even if discrete growth regions are coupled with each other as they grow, anti-phase is generated in the coupling portion. There is an advantage that a region boundary does not occur.
The undulations according to the present invention are not required to have mathematically strictly parallelism or mirror symmetry, and are of a degree sufficient to effectively reduce or eliminate the antiphase region boundary surface. What is necessary is just to have the form of.
[0020]
As a method of forming the undulating shape on the growth target substrate, a plurality of methods such as an optical lithography technique, a press working technique, a laser working, an ultrasonic working technique, and a polishing working technique are exemplified. Whichever method is used, the final form of the surface of the substrate to be grown only needs to have a form sufficient to effectively reduce or eliminate the anti-phase region boundary surface.
If the photolithography technique is used, it is possible to transfer an arbitrary undulating shape to the substrate to be grown by arbitrarily forming a mask pattern to be transferred to the substrate. It is possible to control the width of the undulating shape by changing the line width of the pattern, for example, and to control the depth of the undulating shape and the angle of the slope by controlling the etching selectivity between the resist and the substrate. It is possible. Even when a rectangular pattern shape is disliked, it is possible to form a wavy undulation pattern by softening the resist by heat treatment after pattern transfer to the resist.
If a press working technique is used, an arbitrary undulation shape can be formed on the substrate to be grown by arbitrarily forming a press die. By forming molds of various shapes, various undulating shapes can be formed on the growth target substrate.
When laser processing or ultrasonic processing technology is used, finer processing is possible because the undulating shape is formed directly on the substrate.
If the polishing process is used, the width and depth of the undulating shape can be controlled by changing the size of the abrasive grain and the processing pressure of the polishing. When a substrate having a one-way undulation is to be manufactured, polishing is performed only in one direction.
[0021]
According to the above configuration 2, the effect of the configuration 1 can be ensured and sufficient by performing the epitaxial growth under the growth condition capable of limiting the propagation direction of the film inner surface defect to a specific crystal plane. One of the methods that satisfies this growth condition is, for example, step flow growth.
[0022]
According to Configuration 3, assuming that the average value of the interval between the tops of the undulations on the surface of the growth substrate of silicon carbide is W, the thickness of the silicon carbide film is W / √2 (= 2^1/2), All the anti-phase region boundaries disappear. Therefore, the thickness of the silicon carbide film is W / √2 (= 2^1/2))
In order to obtain the effects of the present invention with a small film thickness, it is desirable that the distance between the tops of the undulations is narrower.
[0023]
In the above configuration 4, the distance between the tops of the undulations, the height difference of the undulations, and the gradient of the undulations are specified.
The distance between the tops of the undulations is preferably 0.01 μm or more from the viewpoint of the limit of the fine processing technique in the production of undulations on the substrate to be grown. If the interval between the tops of the undulations exceeds 10 μm, the frequency of association between the boundary surfaces of the anti-phase regions extremely decreases. Therefore, the interval between the tops of the undulations is desirably 10 μm or less. More preferably, the effect of the present invention is sufficiently exhibited by the interval between the tops of the undulations of 0.1 μm or more and 3 μm or less.
The undulation height difference and interval influence the undulation inclination, that is, the step density. Although the preferred step density varies depending on the crystal growth conditions, it cannot be unconditionally determined.
In the present invention, the effect is exhibited by promoting the growth of silicon carbide in the vicinity of the step at the atomic level on the surface of the substrate to be grown. Therefore, the slope of the undulation is such that the entire slope is covered by a single step. The present invention is realized when the inclination of the (111) plane is 54.7 ° or less. Further, when the inclination is less than 1 °, the step density of the undulating slope is significantly reduced. Therefore, the inclination of the undulating slope is desirably 1 ° or more. More preferably, the effect of the present invention is sufficiently exhibited when the inclination angle of the undulating slope is 2 ° or more and 10 ° or less.
The “undulating slope” in the present invention includes all forms such as a flat surface and a curved surface. Further, the “slope of the slope in the undulation” according to the present invention means a substantial slope of the slope that contributes to the effect of the present invention, and the maximum slope, the average slope, and the like according to the form of the slope. It can be adopted as the "gradient of undulation".
[0024]
Configurations 5 to 7 define the plane orientation of the surface of the silicon carbide growth substrate and the undulation orientation.
When a single-crystal Si (001) plane or a single-crystal cubic silicon carbide (001) plane is used as the plane orientation of the surface of the growth target substrate on which cubic or hexagonal silicon carbide is grown, the direction of expansion of the antiphase region is [110], as shown in FIG. 2, the undulation of the surface is made parallel to any one of these directions (the [1, -1, 0] direction in FIG. 2). As shown, a silicon carbide film is obtained in which the antiphase region boundary surface is effectively eliminated on the axis perpendicular to the undulations (Configurations 5 and 6). In addition, in FIG. 3, W shows the space | interval of an undulation top part.
When a single-crystal hexagonal SiC (1, 1, -2, 0) plane is used as the plane orientation of the surface of the growth target substrate on which cubic or hexagonal silicon carbide is grown, the antiphase expansion direction is [1 , −1, 0, 0], [−1, 1, 0, 0], [0, 0, 0, 1] [0, 0, 0, −1]. Thus, a silicon carbide film in which the anti-phase region boundary surface is effectively eliminated as described above can be obtained (Configuration 7).
[0025]
According to Configuration 8, a silicon carbide film in which the anti-phase region boundary surface is effectively reduced or eliminated can be obtained by using the method described in any of Configurations 1 to 7.
The silicon carbide film of the present invention has very low electrical characteristics because of its low crystal boundary density, and can be suitably used as a semiconductor substrate, a substrate for crystal growth (including a seed crystal), and other electronic elements.
[0026]
According to the above-described Configuration 9, by employing such a substrate structure and a crystal growth method, a silicon carbide film in which the anti-phase region boundary surface is effectively reduced or eliminated can be obtained.
[0027]
【Example】
Hereinafter, the present invention will be described more specifically based on examples.
[0028]
Comparative example
First, in order to confirm the effect of the introduction of the off-angle, SiC (3C-SiC) was used with the Si (001) plane having no off-angle and the Si (001) plane having off-angles of 4 ° and 10 ° as growth substrates. ) Grew. The growth of SiC is divided into a carbonization process on the substrate surface and a SiC growth process by alternate supply of source gases. In the carbonization step, the processed substrate was heated from room temperature to 1050 ° C. for 120 minutes in an acetylene atmosphere. After the carbonization step, dichlorosilane and acetylene were alternately exposed to the substrate surface at 1050 ° C. to grow SiC. Table 1 shows the detailed conditions of the carbonization step, and Table 2 shows the detailed conditions of the SiC growth step.
[0029]
[Table 1]

[0030]
[Table 2]

[0031]
For the SiC grown on each substrate, the density of the anti-phase region boundary surface was measured, and the results shown in Table 3 were obtained.
Note that the density of the anti-phase region boundary surface was obtained by AFM observation of the silicon carbide surface. At this time, the surface of the silicon carbide was subjected to a thermal oxidation treatment, and the thermal oxide film was removed to make the antiphase boundary apparent, and then observation was performed.
[0032]
[Table 3]

[0033]
From the relationship between the off-angle and the anti-phase region boundary surface density shown in Table 3, although the decrease in the anti-phase region boundary surface density due to the introduction of the off-angle is confirmed, it has been found that it has not been completely resolved.
[0034]
FIG. 4 shows a scanning electron micrograph of the surface of the SiC film grown on the substrate having an off-angle of 4 °, and FIG. 5 shows a scanning electron micrograph of the surface of the SiC film grown on the substrate having no off-angle. .
4 and 5, it is confirmed that the terrace area is increased by the introduction of the off-angle, and the SiC growth in the step flow mode is dominant, and the propagation direction of the plane defect is limited to a specific crystal plane. You can see that.
[0035]
Example 1
Using a Si (001) surface as a substrate to be grown, and thermally oxidizing the surface of the substrate, forming a 1.5 μm wide, 60 mm long, 1 μm thick line & space pattern on the surface of the substrate by photolithography using a resist. did. However, the direction of the line & space pattern was parallel to the [110] direction. By heating this substrate using a hot plate under the conditions shown in Table 4, the line & space resist pattern spreads and deforms in the direction orthogonal to the lines, and the top and bottom of the undulation are connected by a smooth curve. The resist pattern shape of the cross section was obtained. The cross-sectional shape (undulation) and planar shape (line & space) of this resist pattern were transferred to a Si substrate by dry etching.
After the resist was removed in a mixed solution of hydrogen peroxide and sulfuric acid (FIG. 6), 3C-SiC was grown. The growth of SiC is divided into a carbonization process on the substrate surface and a SiC growth process by alternate supply of source gases. Table 5 shows the detailed conditions of the SiC growth process. The detailed conditions of the carbonization step were the same as in Table 1.
[0036]
[Table 4]

[0037]
[Table 5]

[0038]
In the SiC growth step, the density of the anti-phase region boundary surface appearing on the outermost surface was measured in the same manner as above by changing the film thickness of SiC by changing the number of supply cycles of the source gas. The results shown were obtained.
[0039]
[Table 6]

[0040]
From the relationship between the SiC film thickness and the anti-phase region boundary surface density shown in Table 6, the film thickness of SiC epitaxially grown on the Si substrate having the undulating shape is 1 / √2 times the interval between the tops of the undulations of 3.0 μm. It can be seen that the reduction of the anti-phase region boundary surface at a point exceeding 2.1 μm is large, and the effectiveness of the present invention is remarkable as compared with the numerical value in Table 3 which is a conventional method.
[0041]
Example 2
Using a Si (001) surface as a substrate to be grown, a line & space pattern having a width of 1.5 μm, a length of 60 mm and a thickness of 1 μm was formed on the surface of the substrate by photolithography using a resist. However, the direction of the line & space pattern was parallel to the [110] direction. The substrate was heated using a hot plate under the conditions shown in Table 7 to soften the resist and change the cross-sectional shape of the resist pattern. The cross-sectional shape (undulation) and the planar shape (line & space) of the resist pattern were transferred to a Si substrate by dry etching.
After removing the resist in a mixed solution of hydrogen peroxide and sulfuric acid, 3C-SiC was grown. The growth of SiC is divided into a carbonization process on the substrate surface and a SiC growth process by alternate supply of source gases. The detailed conditions of the carbonization step were the same as in Table 1, and the detailed conditions of the SiC growth step were the same as in Table 5.
[0042]
[Table 7]

[0043]
The heating temperature of the resist pattern was changed between 150 ° C. and 200 ° C., and 3C-SiC grown on each of the substrates having the undulation inclination angle θ was changed. When the density was measured in the same manner as above, the results shown in Table 8 were obtained.
[0044]
[Table 8]

[0045]
From the relationship between the gradient of the undulation and the density of the anti-phase region boundary surface shown in Table 8, the inclination angle θ of the undulation is particularly less than 54.7 °, which is the angle formed by the (111) plane, and is 1 ° or more. In this case, a decrease in the density of the antiphase region boundary surface can be confirmed. Furthermore, as compared with the values in Table 3 which are the conventional methods, 3C-SiC grown on the undulating substrate as in the present invention has a significantly reduced or eliminated anti-phase region boundary surface density even at the same off-angle. This indicates that the effectiveness of the present invention is remarkable.
[0046]
Example 3
Using a Si (001) surface as a substrate to be grown, a line & space pattern having a width of 1.5 μm, a length of 60 mm and a thickness of 1 μm was formed on the surface of the substrate by photolithography using a resist. However, with respect to the direction of the line & space pattern, the intersection angle ω (see FIG. 7) between the [110] direction and the direction of the line & space pattern was changed as shown in Table 9. Thereafter, the substrate was heated using a hot plate under the heating conditions shown in Table 4 to soften the resist and deform the cross-sectional shape of the resist pattern. This resist pattern shape was transferred to a Si substrate by dry etching.
After removing the resist in a mixed solution of hydrogen peroxide and sulfuric acid, 3C-SiC was grown. The growth of SiC is divided into a carbonization process on the substrate surface and a SiC growth process by alternate supply of source gases. The detailed conditions of the carbonization step were the same as those in Table 1, and the detailed conditions of the SiC growth step were the same as in Table 2.
[0047]
With respect to 3C-SiC grown on each of the substrates where the crossing angle ω was changed, the density of the antiphase region boundary surface appearing on the outermost surface was measured in the same manner as described above, and the results shown in Table 9 were obtained.
[0048]
[Table 9]

[0049]
From the relationship between the intersection angle ω and the anti-phase region boundary surface density shown in Table 9, it can be confirmed that the density of the anti-phase region boundary surface decreases as the direction of the line & space pattern is oriented in the [110] direction. Furthermore, the anti-phase region boundary surface density is significantly reduced or eliminated as compared with the numerical values in Table 3 which is the conventional method, and it can be seen that the effectiveness of the present invention is remarkable.
[0050]
Example 4
In Examples 1 to 3, using a mask having a line and space pattern having the same line width and space width, a substrate having an undulating cross-sectional pattern having the same ratio of concave portions and convex portions was manufactured, and 3C-SiC was grown thereon. Was done. Therefore, in the fourth embodiment, a line and space pattern in which the line width is 1.5 μm and the space width is twice, four times, eight times, and sixteen times the line width is used as the pattern in which the density of the protrusions is reduced. Substrate processing, and 3C-SiC was grown thereon. The substrate processing conditions and the SiC growth conditions are the same as those of the third embodiment. However, the inclination angle of the undulation was 4 °.
When the density of the anti-phase region boundary surface for each pattern in which the density of the undulating concave portions was changed was measured in the same manner as described above, the results shown in Table 10 were obtained. As a comparison, the anti-phase region boundary surface density when a pattern having both a line width and a space width of 1.5 μm is used, and a non-undulating Si (001) which can be regarded as an extreme in which the line width is expanded to infinity (∞) The anti-phase region boundary surface density when a substrate (off angle 0 °) was used was measured in the same manner and shown in Table 10.
[0051]
[Table 10]

[0052]
From Table 10, it can be confirmed that the density of the anti-phase region boundary surface increases as the distance between the undulation convex portions increases and the undulation density decreases. Furthermore, the anti-phase region boundary surface density is significantly reduced or eliminated as compared with the numerical values in Table 3 which is the conventional method, and it can be seen that the effectiveness of the present invention is remarkable.
[0053]
Example 5
In the first to fourth embodiments, only the structure in which the cross section of the substrate is wavy has been described. It is clear from the description of FIG. 3 that the effectiveness of the present invention is maintained for structures other than the wavy type. Actually, undulation processing having a sawtooth cross section was performed on the Si (001) surface by the following method, and 3C-SiC was grown on the substrate.
More specifically, a line & space pattern having a width of 1.5 μm, a length of 60 mm and a thickness of 1 μm was formed on the surface of the substrate by photolithography using a Si (001) surface as a substrate to be grown. However, the direction of the line & space pattern was parallel to the [110] direction. This resist pattern shape was transferred to a Si substrate by dry etching. After the resist was removed in a mixed solution of hydrogen peroxide and sulfuric acid, the substrate was immersed in an aqueous KOH solution to perform wet etching. Table 11 shows the wet etching conditions. As a result of the wet etching, a single-crystal Si (001) plane having sawtooth undulations at inclination angles of 1 °, 10 °, and 55 ° was obtained (see FIG. 8). In FIG. 8, reference numeral 4 denotes a substrate cross-sectional structure before wet etching, and reference numeral 5 denotes a sawtooth-shaped substrate cross-sectional structure after wet etching.
[0054]
[Table 11]

[0055]
3C-SiC was grown on the substrate. The growth of SiC is divided into a carbonization process on the substrate surface and a SiC growth process by alternate supply of source gases. The detailed conditions of the carbonization step were the same as those in Table 1, and the detailed conditions of the SiC growth step were the same as in Table 2.
The density of the anti-phase region boundary surface appearing on the outermost surface of the SiC grown on each substrate was measured in the same manner as described above, and the results shown in Table 12 were obtained.
[0056]
[Table 12]

[0057]
From Table 12, it can be seen that the present invention is effective even when the substrate cross section has a saw-toothed undulating structure. Further, it can be seen that this substrate manufacturing method is suitable for exhibiting the effectiveness of the present invention.
[0058]
Example 6
In each of Examples 1 to 5, a cubic silicon carbide film was grown on a Si (001) plane substrate. In Example 6, as a substrate to be grown, a substrate having undulations extending parallel to the [110] direction on the (001) plane of single-crystal cubic silicon carbide (single-crystal 3C-SiC), and a single-crystal hexagon A substrate having undulations extending parallel to the [0,0,0,1] direction on the (1,1, -2,0) plane of crystalline silicon carbide, and cubic A silicon carbide film or a hexagonal silicon carbide film was grown.
As a result, the effectiveness of the present invention was confirmed as in Examples 1 to 5.
[0059]
Example 7
In all of Examples 1 to 6, the method of etching the surface of the Si substrate (001) by using the lithography technique is employed as the method of forming the undulation. Can be performed by a method other than etching. A seventh embodiment will be given as an example.
A Si (001) surface was used as a substrate, and this surface was thermally oxidized to form a 3000 Å Si oxide film (SiO 2 film).₂Film) was formed. A line and space pattern having a width of 1.5 μm, a length of 60 mm, and a thickness of 1 μm was formed on the thermal oxide film by using a photolithography technique. However, the direction of the line & space pattern was parallel to the [110] direction. This resist pattern shape is transferred to a thermal oxide film by dry etching and striped SiO 2₂A pattern and an exposed Si portion were provided. After removing the resist in a mixed solution of hydrogen peroxide and sulfuric acid, selective homoepitaxial growth of Si was performed on the substrate as shown in FIG. Table 13 shows detailed conditions of the SiC growth process. In FIG. 9, reference numeral 6 denotes a stripe-shaped SiO₂Pattern 7 indicates a Si layer that has been selectively homoepitaxially grown.
[0060]
[Table 13]

[0061]
As a result of the Si growth, a single crystal Si (001) plane having undulations with a tilt angle of 55 ° was obtained. 3C-SiC was grown on the substrate surface, and it was confirmed that the density of the anti-phase region boundary surface was significantly reduced.
[0062]
Example 8
In Example 8, an attempt was made to fabricate an undulating substrate parallel to the [110] direction by polishing the surface of the Si (100) substrate in parallel to the [110] direction. For polishing, a commercially available diamond slurry having a diameter of about 15 mmφ (manufactured by Engis: High Press) and a commercially available polishing pad (manufactured by Engis: M414) were used.
The diamond slurry is uniformly infiltrated on the pad, a Si (100) substrate is placed on the pad, and 0.1 to 0.2 kg / cm²Was applied to the entire Si (100) substrate, and reciprocated 300 times a distance of about 20 cm above the pad in parallel with the [110] direction to perform a unidirectional polishing treatment. Innumerable polishing scratches (scratches) parallel to the [110] direction were formed on the surface of the Si (100) substrate.
Since abrasive grains and the like are attached to the surface of the Si (100) substrate subjected to the one-way polishing, NH₄OH + H₂O₂+ H₂O mixed solution (NH₄OH: H₂O₂: H₂O = 4: 4: 1 at a liquid temperature of 60 ° C.)₂SO₄+ H₂O₂Solution (H₂SO₄: H₂O₂(1: 1: 1 liquid temperature of 80 ° C.) and HF (10%) solution alternately three times to wash, and finally rinsed with pure water.
After the cleaning, a thermal oxide film was formed on the one-way polished substrate to a thickness of about 5000 angstroms. The thermal oxide film was removed with a HF 10% solution. If only polishing is performed, the substrate surface has many fine irregularities and defects other than scratches, and it is difficult to use as a substrate to be grown. However, by forming a thermal oxide film once and removing the oxide film again, fine irregularities on the substrate surface were removed, and a very smooth undulation (undulating) surface could be obtained. Looking at the wavy cross section, the size of the wavy irregularities is unstable and irregular, but the density is high. At least there is no horizontal surface. It is always undulating. On average, the groove had a depth of about 30 to 50 nm and a width of about 0.5 to 1.5 μm. The slope was 3-5 degrees.
Using this substrate, a SiC film was formed on the substrate. As a result, the effect of the undulating substrate parallel to [110] was obtained. That is, defects at the antiphase boundary surface are greatly reduced.
For example, the anti-phase boundary surface density of a SiC film grown on an unpolished Si substrate is 8 × 10⁹Pieces / cm²On the other hand, the anti-phase boundary surface defect density of the SiC film grown on the unidirectionally polished Si substrate is 0 to 1 defect / cm.²Becomes The undulation shape and the anti-phase boundary surface defect density with respect to the abrasive grain size are as shown in Table 14. Table 15 shows the undulation density and the antiphase boundary surface defect density with respect to the number of times of polishing.
[0063]
[Table 14]

[Table 15]

[0064]
In Example 8, a diamond slurry having a size of 15 μmφ was used as an abrasive, but the size and type of abrasive grains are not limited thereto. The pad is not limited to the above. The load pressure between the substrate and the pad during polishing, the polishing rate and the number of times are not limited to those described above. Further, although Si (100) was used in Example 8, it goes without saying that the same result as described above can be obtained by using cubic SiC or hexagonal SiC.
[0065]
Although the present invention has been described with reference to the embodiments, the present invention is not limited to the above embodiments.
[0066]
For example, the film forming conditions and the film thickness of the silicon carbide film are not limited to those of the embodiment.
[0067]
As the substrate to be grown, for example, a single crystal substrate such as silicon carbide or sapphire can be used.
[0068]
As a raw material gas for silicon, dichlorosilane (SiH₂Cl₂) But SiH₄, SiCl₄, SiHCl₃For example, a silane-based compound gas such as this can be used. In addition, acetylene (C₂H₂) But CH₄, C₂H₆, C₃H₈Hydrocarbon gas such as can be used.
[0069]
The silicon carbide epitaxial growth method may be any method as long as the propagation direction of the inner surface defect of the film can be limited to a specific crystal plane. Alternatively, a molecular beam epitaxy (MBE) method or the like can be used. Further, in the case of the CVD method, a simultaneous supply method of the source gas can be used instead of the alternate supply method of the source gas.
[0070]
The silicon carbide film formed on the substrate to be grown by the method of the present invention is formed by bonding the surface of the silicon carbide film to an insulator, removing the substrate to be grown, and then forming a defect layer on the silicon carbide film. By removing the portion having the anti-phase region boundary surface density), an SOI (semiconductor-on-insulator) structure in which a semiconductor thin film is formed over an insulator can be obtained.
[0071]
Here, the bonding between the silicon carbide film and the insulator can be performed by a method such as anodic bonding, bonding with low-melting glass, direct bonding, or bonding with an adhesive. The anodic bonding is performed by using a glass containing charge-transferable ions (for example, silicate glass, borosilicate glass, borate glass, aluminosilicate glass, phosphate glass, or fluorophosphate glass) and a silicon carbide film. Are brought into contact with each other, and then an electric field is applied to join them. In this case, the bonding temperature is 200 to 300 ° C., the applied voltage is 500 to 1000 V, and the load is 500 to 1000 g / cm.²It is about. Bonding with low-melting glass is a method in which low-melting glass is deposited on the surface of a silicon carbide film by sputtering or the like, and a load and heat are applied to bond the glasses together. Direct bonding is a method in which a silicon carbide film is directly contacted and bonded to glass by electrostatic force, and then a load and heat are applied to strengthen the bonding at the interface.
[0072]
The removal of the growth target substrate can be performed by, for example, wet etching. For example, removal of a silicon substrate is performed by using HF and HNO₃Mixed acid (HF: HNO₃= 7: 1).
[0073]
The removal of the defect layer is performed for the purpose of removing a defect layer in which an antiphase boundary exists at a high density near the substrate interface of the silicon carbide film. The removal of the defective layer can be performed by, for example, dry etching. For example, CF₄(40sccm), O₂(10 sccm) is used as an etching gas, and the defect layer can be removed by performing reactive ion etching at an RF power of 300 W.
[0074]
Applications of the SOI structure (substrate) include, for example, a transparent conductive film in a semiconductor substrate, a TFT liquid crystal substrate, a Kerr effect dielectric layer in a magneto-optical recording medium, a micromachine, various sensors (such as a stress sensor), X And a line-permeable film.
[0075]
【The invention's effect】
As described above, according to the method for manufacturing silicon carbide of the present invention, a silicon carbide film in which the anti-phase region boundary surface is effectively reduced or eliminated can be obtained.
In addition, the silicon carbide film of the present invention has very low electrical characteristics due to a low crystal boundary density, and is widely useful as various electronic devices.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view for explaining the occurrence and disappearance of an anti-phase region boundary surface accompanying 3C-SiC growth on a Si substrate having an off angle.
FIG. 2 is a perspective view showing a single-crystal Si (001) plane substrate provided with undulations parallel to the [1, -1, 0] direction.
FIG. 3 is a schematic cross-sectional view for explaining disappearance of an anti-phase region boundary surface accompanying 3C-SiC growth on an undulating Si (001) plane substrate.
FIG. 4 is a scanning electron micrograph of the surface of a SiC film grown on a substrate having an off angle of 4 °.
FIG. 5 is a scanning electron micrograph of the surface of a SiC film grown on a substrate having no off-angle.
FIG. 6 is a scanning electron micrograph of an undulated Si substrate.
FIG. 7 is a perspective view schematically showing an Si substrate processed by shifting the direction of a relief pattern from a [110] direction.
FIG. 8 is a cross-sectional view schematically showing a surface of a Si substrate having a serrated undulation.
FIG. 9 is a schematic cross-sectional view for explaining a method of forming undulations by a method other than etching.
[Explanation of symbols]
1 Anti-phase region boundary generated in single atom step of Si substrate
2 Anti-phase region boundary junction
3 Anti-phase region boundary surface generated on the surface terrace of the Si substrate
θ off angle
Angle (55 °) between φ Si (001) plane and boundary surface of antiphase region
W Spacing between undulating tops
ω intersection angle
4 Cross-sectional structure of substrate before wet etching
5. Sawtooth-shaped substrate cross-sectional structure after wet etching
6 Striped SiO₂pattern
7 Selective homoepitaxially grown Si layer

Claims (15)

A method for producing a silicon carbide film in which silicon carbide is epitaxially grown on a single crystal substrate surface by inheriting its crystal orientation,
As the substrate,
A substrate having a plurality of undulations extending in one direction parallel to all or a part of the substrate surface, wherein both side surfaces of each undulation are inclined surfaces,
A method for manufacturing a silicon carbide film, comprising growing silicon carbide on the substrate surface. 2. The method for manufacturing a silicon carbide film according to claim 1, wherein an epitaxial growth mechanism capable of limiting the propagation direction of a plane defect generated in the silicon carbide film to a specific crystal plane during growth is used. The method according to claim 2, wherein the surface defect is an anti-phase region boundary surface. 4. The method of manufacturing a silicon carbide film according to claim 1, wherein the undulation is formed by directly processing an undulation shape on the substrate. The method according to claim 1, wherein the undulations are formed by performing a polishing process on the surface of the substrate. The thickness of the silicon carbide film is equal to or more than W / √2 (= 2 ^1/2 ), where W is the average value of the interval between the tops of the undulations on the substrate surface. 5. The method for manufacturing a silicon carbide film according to any one of 5. The interval between the tops of the undulations on the substrate surface is 0.01 μm or more and 10 μm or less, the height difference between the undulations is 0.01 μm or more and 20 μm or less, and the slope of the slope in the undulations is 1 ° or more and 55 ° or less. The method for manufacturing a silicon carbide film according to claim 1, wherein: The substrate is Si, and the surface of the substrate is ( 001 ) The method for manufacturing a silicon carbide film according to claim 1, wherein the surface is a surface. The substrate is the substrate surface ( 001 ) On the surface, [ 110 ] The method for producing silicon carbide according to claim 8, further comprising undulations extending parallel to the direction. The substrate according to claim 1, wherein the substrate is single-crystal SiC, the substrate surface is a (001) plane, and the surface has undulations extending in parallel to the [110] direction. 3. The method for producing a silicon carbide film according to item 1. The substrate according to claim 1, wherein the substrate is single crystal 3C—SiC, the surface of the substrate is a (001) plane, and the surface has undulations extending parallel to the [110] direction. The method for producing a silicon carbide film according to any one of the above. The substrate is hexagonal single-crystal SiC, the substrate surface is a (1,1, -2,0) plane, and the surface has a [1, -1,0,0] orientation or [0,0, 8. The method for manufacturing a silicon carbide film according to claim 1, wherein the silicon carbide film has undulations extending parallel to the [0, 1] direction. The method for manufacturing the silicon carbide film according to any one of claims 1 to 12, wherein the substrate section is undulating structure or cross section has a sawtooth relief. 14. The method of manufacturing a silicon carbide film according to claim 1, wherein silicon carbide is grown on the substrate surface by alternately supplying carbon and silicon source gases. The method of manufacturing a silicon carbide film according to claim 1, further comprising a step of carbonizing the surface of the substrate before growing the silicon carbide on the surface of the substrate.

Images